Platform-train interface (PTI) is a shared space with several interactions between travellers. These interactions lead to congestion, delays, safety concerns at PTI and resulting in a negative experience for users. Understanding individual behaviour is crucial to improving pedestrian flow at stations and users’ experience, to fine supporting public transport use. This study aims to understand how individuals experience and behaviour at PTI. Specifically, we investigate psychological comfort and its link with approach/avoidance strategies (AAS) used by travellers at PTI. Based on the critical incidents technique, 22 interviews were conducted. Participants were asked to describe multiple trips according to their valence (positive v. negative). Seventy-seven critical incidents representing 125 route sections involving a station were collected, coded and analysed through multiple correspondence analysis (MCA), to determine reasons of incidents’ valence. The descriptive analysis of the 125 sections aims at identifying AAS used by individuals at PTI. Results suggest that reasons of the valence of the trip (e.g., security or density) could be related to the different psychological comfort’s dimensions. AAS reported seem to be aimed at increasing psychological comfort. Finally, we observed that while crowds usually link to avoidance strategies, in specific cases of uncertainty travellers also reported approaching a crowd.

International audience

Our research aims at understanding the various forms of participation in Open Source Software (OSS) design, seen as distributed design in online spaces of actions–discussion, implementation, and boundary between these spaces. We propose a methodology—based on situated analyses of a formal design process used in the Python project—to identify the distribution of actual roles (implementation, interactive, group, and design oriented) performed by participants into and between the spaces (defining boundary spaces). This notion of roles is grounded in collaborative design activities performed online by participants. This way, our findings complete the core-periphery model of participation in OSS. Concerning the distribution of roles between spaces, we reveal a map of participation in OSS: The majority of participants are pure discussants, but all participants in the implementation spaces do also act in the discussion space, and few participants act at boundary spaces. Concerning the distribution of roles between participants in the discussion space, we reveal that interactions are structured by a central hub (occupied by key participants) and that, whereas design-oriented roles are spread among all participants, group-oriented roles are performed by one or two participants in the respective spaces and at their boundary. Finally, combination of roles reveals five individual profiles performed by participants. Our approach could be extended to other design situations to explore relationships between forms of participation—in particular, those revealing use-oriented contributions—performance, and quality of the design product. Finally, it could be a basis for specifying tools to monitor and manage community activity for both research issues and support of online community.

A growing number of empirical studies evaluate the influence of Mental Health (MH) technology on the clinical effectiveness, the therapeutic relationship (i.e., therapeutic alliance), and usability issues. However, to the authors’ knowledge, no studies have yet been performed regarding the influence of technology on the therapeutic process in terms of collaboration. This study evaluates the quality of collaboration between the client and therapist in Augmented Reality Exposure Therapy (ARET) context and the traditional, In Vivo Exposure Therapy (IVET) context with the Therapeutic Collaborative Scale (TCS). Twenty participants received an intensive session of cognitive behavioral therapy in either a technology-mediated therapeutic context or in a traditional therapeutic context. The results indicate that both therapeutic conditions show high collaboration scores. However, the asymmetry of roles between the therapist and the client under both conditions were detected. Also, a greater level of distraction was observed for therapists in ARET, which affected the quality of the therapists’ involvement in the therapeutic session. The implications of these results are discussed.

This paper presents our virtual environment for training at high-risk sites (SEVESO sites). In order to enhance this environment, we have integrated into it an intelligent tutoring system called HERA. This system uses the print trace to which the learning process gives rise, and produces an activity trace using plan-recognition techniques. In this paper we present the main components (modules, models) of HERA, and its features for tracking the learner. We explain how HERA retrieves data and transmits them to the learner and the trainer. The data concern the task realized, the errors committed and their type, the potential risks, and comments and explanations about the errors and risky situations.

Anaesthesia is a medical act which eliminates the feeling of pain as well as the motor reactions of a person, before performing a surgical operation. Loco-Regional Anaesthesia (LRA) concerns only a part of the body such as the front arm or leg. This practice is increasingly used today notably because the patient can remain conscious and can recover more rapidly. However, LRA still remains a risky procedure. In this paper, we introduce a novel medical simulator called SAILOR for the training for LRA with neurostimulation. SAILOR is based on desktop virtual reality, realistic 3-D rendering and interactive techniques with a classical mouse and keyboard. It simulates the various biological phenomena which can occur during an anaesthesia procedure. We also introduce a novel pseudo-haptic effect to enhance the palpation of the virtual patient's body and feel the inner organs. The first feedback from users of the commercialized DVD version of SAILOR as well as the results of pilot tests suggest that this simulator is a very promising tool for education and training for LRA.

This paper is an analysis of online discussions in an Open Source Software (OSS) design community, the Python project. Developers of Python are geographically distributed and work online asynchronously. The objective of our study is to understand and to model the dynamics of the OSS design process that takes place in mailing list exchanges. We develop a method to study distant and asynchronous collaborative design activity based on an analysis of quoting practices. We analyze and visualize three aspects of the online dynamics: social, thematic temporal, and design. We show that roles emerge during discussions according to the involvement and the position of the participants in the discussions and how they influence participation in the design discussions. In our analysis of the thematic temporal dynamics of discussion, we examine how themes of discussion emerge, diverge, and are refined over time. To understand the design dynamics, we perform a content analysis of messages exchanged between developers to reveal how the online discussions reflect the “work flow” of the project: it provides us with a picture of the collaborative design process in the OSS community. These combined results clarify how knowledge and artefacts are elaborated in this epistemic, exploration-oriented, OSS community. Finally, we outline the need to automate of our method to extend our results. The proposed automation could have implications for both researchers and participants in OSS communities.

In previous work on so-called pseudo-haptic textures, we investigated the possibility of simulating sensations of texture without haptic devices by using the sole manipulation of the speed of a mouse cursor (a technique called speed technique). In this paper, we describe another technique (called Size technique) to enhance the speed technique and simulate texture sensations by varying the size of the cursor according to the local height of the texture displayed on the computer screen. With the size technique, the user would see an increase (decrease) in cursor size corresponding to a positive (negative) slope of the texture. We have conducted a series of experiments to study and compare the use of both the size and speed technique for simulating simple shapes like bumps and holes. In Experiment 1, our results showed that participants could successfully identify bumps and holes using the size technique alone. Performances obtained with the size technique reached a similar level of accuracy as found previously with the speed technique alone. In Experiment 2, we determined a point of subjective equality between bumps simulated by each technique separately, which suggests that the two techniques provide information that can be perceptually equivalent. In Experiment 3, using paradoxical situations of conflict between the two techniques, we have found that participants' answers were more influenced by the size technique, suggesting a dominance of the size over the speed technique. Furthermore, we have found a mutual reinforcement of the techniques, i.e., when the two techniques were consistently combined, the participants were more efficient in identifying the simulated shapes. In Experiment 4, we further observed the complex interactions between the information associated with the two techniques in the perception and in the decision process related to the accurate identification of bumps and holes. Taken together, our results promote the use of both techniques for the low-cost simulation of texture sensations in applications, such as videogames, internet, and graphical user interfaces.

This paper describes an experiment conducted to study the influence of visual appearance of user's avatar (or 3D cursor) on the manipulation of virtual objects in virtual environments (VE). Participants were asked to pick up a virtual cube and place it at a random location in a VE. We found that one visual property of the avatar (the presence or absence of a directional cue) could influence the way participants picked up the cube in the VE. When using an avatar or a 3D cursor with a strong directional cue (e.g., arrows pointing to the left or right), participants generally picked up the cube by a specific side (e.g., right or left side). When using 3D cursors with no main directional cue, participants more frequently picked up the virtual cube by its front or top

This paper describes a new interaction technique called haptic hybrid rotations to overcome the physical angular limitations of force-feedback devices when manipulating virtual objects. This technique is based on a hybrid control of the object manipulated with the device. When approaching the angular mechanical stops of the device, the control mode switches from angular position-control to rate-control. The forcefeedback of the device is used to simulate the use of an elastic device in the rate-control mode. An experiment was carried out to compare this technique with two other common alternatives that are used when manipulating virtual objects with force-feedback devices: rotations scaling, and the clutching technique. Our results showed that haptic hybrid rotations were both the fastest and the most appreciated technique for the proposed experiment.

This paper investigates the use of camera motions, in order to improve the sensation of walking in a Virtual Environment. A simple model of camera motion is first proposed. This model uses: (1) oscillating motions for the position of the camera, and (2) a compensation motion which changes the orientation of the camera and simulate oculomotor compensation to keep a constant focal point when walking. Then we describe two experiments which were conducted to study the characteristics of our model and the preference of the users in terms of sensation of walking. The first experiment compared the use of oscillating camera motions along the three directions of space. The oscillating motions were all preferred to the control condition (i.e. a linear motion, as if the user was driving a car). Furthermore, the participants preferred oscillating motions along the vertical axis, compared with the two other directions of space. The second experiment was focused on the use of a compensation motion. It showed that on average participants preferred a compensated motion during the walk, as compared with a motion with a constant orientation of the camera. These results are consistent with the way our body and eyes move naturally when walking in real life. Taken together, our results suggest that camera motions can considerably improve the sensation of walking in virtual environments. Camera motions could be further introduced in numerous applications of virtual reality in which the simulation of walking is important, such as: architectural visits, training simulations, or videogames.

This paper presents an analysis of online discussions in Open Source Software (OSS) design. The objective of our work is to understand and model the dynamics of OSS design that take place in mailing list exchanges. We show how quotation practices can be used to locate design relevant data in discussion archives. OSS developers use quotation as a mechanism to maintain the discursive context. To retrace thematic coherence in the online discussions of a major OSS project, Python, we follow how messages are linked through quotation practices. We compare our quotation-based analysis with a more conventional analysis: a thread-based of the reply-to links between messages. The advantages of a quotation-based analysis over a thread-based analysis are outlined. Our analysis reveals also the links between the social structure and elements in the discussion space and how it shapes influence in the design process.

This paper describes the use and characteristics of a virtual reality system called the Virtual Technical Trainer (VTT). This system is dedicated to vocational training courses on using and programming numerically-controlled milling machines. It aims at replacing the conventional mechanical milling machines which are currently used in such vocational training courses. VTT proposes an interactive manipulation of a cutter of a virtual milling machine, with visual, audio and haptic (force) feedback. VTT uses a haptic device which was specifically designed for the purpose of our pedagogical application. When the virtual cutter mills a piece of material, a plastic deformation algorithm is used and the material is progressively carved. Trainees can feel the cutting effort thanks to a force feedback which varies as a function of different simulation parameters (rotation speed of the tool, type of material to carve, etc). Realistic audio feedback (which was recorded in real situations) and additional visual assistances may be added, in order to increase the perception and understanding of the milling task. A preliminary evaluation of VTT showed that this simulator could be used by vocational trainers successfully. It could help them to teach the basic principles of machining at the first stages of vocational training courses on numerically-controlled milling machines. 1

This paper describes two psychophysical experiments which were conducted to evaluate the influence of the control/display (C/D) ratio on the perception of mass of manipulated objects in virtual environments (VE). In both experiments, a discrimination task was used in which participants were asked to identify the heavier object between two virtual balls. Participants could weigh each ball via a haptic interface and look at its synthetic display on a computer screen. Unknown to the participants, two parameters varied between each trial: the difference of mass between the balls and the C/D ratio used in the visual display when weighing the comparison ball. The data collected demonstrated that the C/D ratio significantly influenced the result of the mass discrimination task and sometimes even reversed it. The absence of gravity force largely increased this effect. These results suggest that if the visual motion of a manipulated virtual object is amplified when compared to the actual motion of the user's hand (i.e. if the C/D ratio used is smaller than 1), the user tends to feel that the mass of the object decreases. Thus, decreasing or amplifying the motions of the user in a VE can strongly modify the perception of haptic properties of objects that he/she manipulates. Designers of virtual environments could use these results for simplification considerations and also to avoid potential perceptual aberrations.

We present a new interaction technique to simulate textures in desktop applications without a haptic interface. The proposed technique consists in modifying the motion of the cursor on the computer screen - i.e. the Control/Display ratio. Assuming that the image displayed on the screen corresponds to a top view of the texture, an acceleration (or deceleration) of the cursor indicates a negative (or positive) slope of the texture. Experimental evaluations showed that participants could successfully identify macroscopic textures such as bumps and holes, by simply using the variations of the motion of the cursor. Furthermore, the participants were able to draw the different profiles of bumps and holes which were simulated, correctly. These results suggest that our technique enabled the participants to successfully conjure a mental image of the topography of the macroscopic textures. Applications for this technique are: the feeling of images (pictures, drawings) or GUI components (windows' edges, buttons), the improvement of navigation, or the visualization of scientific data.

Application control in virtual environments (VE) is still an open field of research. The Command and Control Cube (C/sup 3/) developed by Grosjean et al. (2001) is a quick access menu for the VE configuration called workbench (a large screen displaying stereoscopic images). The C/sup 3/ presents two modes, one with the graphical display of the cubic structure associated to the C/sup 3/ and a blind mode for expert users, with no feedback. We conduct formal tests of the C/sup 3/ under four different conditions: the visual mode with the graphical display, the blind mode with no feedback and two additional conditions enhancing the expert blind mode: a tactile mode with the tactile feedback, of a Cyberglove/spl trade/ and a sound mode with a standard audio device. Results show that the addition of sound and tactile feedback is more disturbing to the users than the blind mode. The visual mode performs the best although the blind mode achieves some promising results.

Describes a psychophysical experiment designed to study the phenomenon of illusion which occurs with pseudo-haptic feedback, and to identify the moment when this illusion occurs: the "boundary of illusion". The subjects were given the task of deciding which of two virtual springs is the stiffer, these springs being simulated with a PHANToM/sup TM/ force feedback device and displayed on a monoscopic computer screen. The first spring had a realistic behavior, since its visual and haptic displacements were identical. The second spring-the pseudo-haptic one-was stiffer on a haptic basis, but sometimes less stiff on a visual basis. The data collected allowed us to calculate the visual point of subjective equality (PSE) between the two springs, which represents the boundary of the sensory illusion. On average, a high value of PSE turned out to be -24%. This value increased monotonically when the haptic difference between the springs increased. This implies that more visual deformation is necessary to compensate for large haptic differences and qualifies the notion of visual dominance. However, this boundary varies greatly depending on the subjects and their sensory integration strategy. The subjects were sensitive to this illusion to varying degrees. They were divided into different populations-from those who were "haptically oriented" to those who were "visually oriented".